1. Field of the Invention
The field of this invention is in valves for fluid and gas flow, particularly natural gas.
2. Related Art
The flow of the fluids and gases being piped through lines is typically controlled with valves. The valves of course control flow through a pipe by obstructing the pipe in one form or another. In the prior art, the form of obstruction is asymmetrical. For example if a simple screw or needle type valve mechanically advances a gate or needle into a cylinder from one side. Even well-known butterfly valves are symmetrical in one direction, but asymmetrical in another, in that half of the butterfly disk advances towards the source of flow while the other half recedes away from it.
The effect on the flow of the fluid gases that is created by the simple mechanical devices is also asymmetrical, irregular and unpredictable. Generally, it is desirable to have more symmetrical fluid flow throughout the range of constriction that a valve is designed to achieve. This promotes a more rapid return to laminar flow, reduces friction, avoids obstruction from contaminants, reduces back pressure and enables more accurate flow rate and pressure control. More particularly, in some applications, particularly pressurized applications for gas, there is a desirability and need for a symmetrical and therefore more precise constriction of gas flow in order to promote predictably and accuracy of use of the gas thereby making its use more economical across all ranges of pressure and volume to be executed by the valve.
Most particularly, some applications of natural gas use, for example, heat treatment of production material, most especially heat treatment of ferrous metals, requires an optimally precise control of gas flow. More particularly still, a gas flow is combined with gas or air in order to achieve a precise control of how lean or rich will be the output of the gas line for combustion in the heat treating chamber. Precise control of how lean or rich the gas output into the heating chamber is important because the chemical and rheological properties of the metal being treated are sensitive to the chemical atmosphere in the chamber which in turn is dependent upon the gas/air mixture received from the gas line.
FIG. 1, depicting a prior art natural gas burner assembly (10) shows the natural gas line (12) in combination with an air or oxygen line (14). The air line (14) is controlled by a butterfly valve (16). Downstream of the butterfly valve, a flow sensor control (18) controls an impulse valve (20) in the gas line (10). If any fine adjustment is needed, a needle valve (22) is fitted downstream of gas line (10). This is an example of an unintegrated assembly created from separate components. A disadvantage of such an assembly is that the final output does not vary proportionally with adjustment of controls. In prior art valves, such as valve 16 in FIG. 1, the amount of flow allowed to pass varies with opening in an unpredictable fashion that is not continuously proportional to the progressive opening or closing of the valve. The volume, pressure and turbulence of flow are not mathematically predictable or precisely controllable. Accordingly, in the prior art application illustrated, the mixture of the gas/air combination is also unpredictable and poorly controlled. The volume of flow as a function of the percentage of opening of a valve is complex, difficult to model, variable over time and sometimes discontinuous.
There is a need in the art for a valve that opens and closes in a manner that will increase or decrease flow of the fluid or gas to the valve in a mathematically predictable, controlled fashion that is proportionate to the percentage of the opening or closing of the valve. There is a continuing need in the art for durability, efficiency, integration of components, type of sealing to prevent leaks, economy and durability.